S‐Glutathionylation of troponin I (fast) increases contractile apparatus Ca2+ sensitivity in fast‐twitch muscle fibres of rats and humans

Key points  •  Reactive oxygen‐based molecules generated within muscle fibres in both exercise and pathological conditions can greatly affect muscle function. These and consequent reactions can lead to either decreased or increased force response by the contractile proteins, but the mechanisms are u...

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Bibliographic Details
Published in:The Journal of physiology 2012-03, Vol.590 (6), p.1443-1463
Main Authors: Mollica, J. P., Dutka, T. L., Merry, T. L., Lamboley, C. R., McConell, G. K., McKenna, M. J., Murphy, R. M., Lamb, G. D.
Format: Article
Language:English
Subjects:
2,2'-Dipyridyl - analogs & derivatives
2,2'-Dipyridyl - pharmacology
Adult
Amphibia
Animals
Bufo marinus
Calcium
Calcium - physiology
Calcium buffering
Chickens
Cysteine
Cysteine - physiology
Disulfides - pharmacology
Exercise - physiology
Female
Glutathione
Glutathione - pharmacology
Glutathione Disulfide - pharmacology
Humans
Light chains
Male
Muscle contraction
Muscle Contraction - drug effects
Muscle Contraction - physiology
Muscle Fibers, Fast-Twitch - drug effects
Muscle Fibers, Fast-Twitch - physiology
Muscle Fibers, Slow-Twitch - drug effects
Muscle Fibers, Slow-Twitch - physiology
Muscles
Myosin
N-Ethylmaleimide
Oxidation
Oxygen consumption
pH effects
Physical training
Rabbits
Rats
Rats, Long-Evans
Rodents
Skeletal muscle
Skeletal Muscle and Exercise
Skin
Swine
Troponin C
Troponin I
Troponin I - physiology
Western blotting
Young Adult
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Summary:Key points  •  Reactive oxygen‐based molecules generated within muscle fibres in both exercise and pathological conditions can greatly affect muscle function. These and consequent reactions can lead to either decreased or increased force response by the contractile proteins, but the mechanisms are unknown. •  This study demonstrates that the increase in force response appears to be due to a specific chemical process, known as S‐glutathionylation, of a particular cysteine residue present on the troponin I molecule in fast‐twitch muscle fibres, which is involved in sensing and responding to changes in intracellular calcium levels. •  S‐Glutathionylation can occur when glutathione, the primary cellular anti‐oxidant, reacts with oxidized cysteine residues. •  S‐Glutathionylation of troponin I not only helps protect the molecule from oxidative stress, but evidently also makes the contractile apparatus much more sensitive to calcium ions. •  This process seemingly occurs in exercising humans and is likely to be an important mechanism helping delay onset of muscle fatigue.   Oxidation can decrease or increase the Ca2+ sensitivity of the contractile apparatus in rodent fast‐twitch (type II) skeletal muscle fibres, but the reactions and molecular targets involved are unknown. This study examined whether increased Ca2+ sensitivity is due to S‐glutathionylation of particular cysteine residues. Skinned muscle fibres were directly activated in heavily buffered Ca2+ solutions to assess contractile apparatus Ca2+ sensitivity. Rat type II fibres were subjected to S‐glutathionylation by successive treatments with 2,2′‐dithiodipyridine (DTDP) and glutathione (GSH), and displayed a maximal increase in pCa50 (−log10[Ca2+] at half‐maximal force) of ∼0.24 pCa units, with little or no effect on maximum force or Hill coefficient. Partial similar effect was produced by exposure to oxidized gluthathione (GSSG, 10 mm) for 10 min at pH 7.1, and near‐maximal effect by GSSG treatment at pH 8.5. None of these treatments significantly altered Ca2+ sensitivity in rat type I fibres. Western blotting showed that both the DTDP–GSH and GSSG–pH 8.5 treatments caused marked S‐glutathionylation of the fast troponin I isoform (TnIf) present in type II fibres, but not of troponin C (TnC) or myosin light chain 2. Both the increased Ca2+ sensitivity and glutathionylation of TnIf were blocked by N‐ethylmaleimide (NEM). S‐Nitrosoglutathione (GSNO) also increased Ca2+ sensitivity, but only in condition
ISSN:0022-3751
1469-7793
DOI:10.1113/jphysiol.2011.224535